array property stops script execution

I have followed Bill Cheeseman sampe code “pairs” to script mu Objective C application called “SolarMaxOsX”
In Objective C code I have used message logs to understand what happens.

Below the error I get:

tell application "/Users/guydesbief/Library/Developer/Xcode/DerivedData/SolarMaxOsX-cgcuhyptmpmtiegixfnbbhpexjhn/Build/Products/Debug/" to activate
-- delay 30
tell application "/Users/guydesbief/Library/Developer/Xcode/DerivedData/SolarMaxOsX-cgcuhyptmpmtiegixfnbbhpexjhn/Build/Products/Debug/"
	--	set nomAppli to the name of application
	--	set theWindows to windows
	class of onduleurs
	count of onduleurs
	--	get properties
	set NbWin to the count of windows
	set theWindow to first item of windows
	properties of the theWindow
	tell window "UPS Sumary"
		--click on "Statistics button"
		-- click  on button 1 of theWindow
		--		set enabled of button1 to true
	end tell
	get properties
	get id of first onduleur of onduleurs
The results in appleScript:
tell application "SolarMaxOsX"
	get class of every onduleur
		--> {onduleur, onduleur, onduleur}
	count every onduleur of current application
		--> 3
	count every window of current application
		--> 1
	get item 1 of every window
		--> window id 9796
	get properties of window id 9796
		--> {closeable:true, zoomed:false, class:window, index:1, visible:true, name:"UPS Sumary", miniaturizable:true, id:9796, miniaturized:false, resizable:true, bounds:{30, 28, 530, 576}, zoomable:true}
	get properties
		--> error number -10000
Résultat :
error "Erreur dans SolarMaxOsX : Le gestionnaire AppleEvent a échoué." number -10000

It seems that my objectSpecifier method in Ups Category (or Ups class) is never called

[b]I wonder if there is not a coercion to make between AppleScript onduleur class to real Objective C Ups class

Thanks for your answers[/b]